1. Technical Field
This invention relates, generally, to the art of making rigid panels. More particularly, it relates to the art of making thin panels having urethane cores. It also relates to a flexible hinge construction that enables edge-to-edge hinged interconnection of display panels.
2. Description of the Prior Art
Rigid panels are used in a wide variety of ways. Sales personnel, for example, often build information displays that employ such panels. Since sales personnel often travel extensively, it is important that the display panels they use be light in weight and easily transportable. Moreover, it is important that the panels be easily deployed and that the display, when fully set up, is attractive.
Most display panels are rectangular in configuration and are usually a little more than a centimeter in thickness. The flat display surfaces are usually covered by a suitable material.
The core of a typical display panel might be made of expanded polystyrene because that material is light in weight and reasonably durable, but the manufacturing of polystyrene is apparently detrimental to the ozone layer and efforts are under way to ban such manufacturing. Another common core material is corrugated cardboard, but the peripheral edges of display panels made from that material are unsightly.
Panels having urethane foam cores have also been made, but such panels are usually more than seven centimeters in thickness; accordingly, such panels are commonly used in the construction of walk-in freezers or refrigerators.
Attempts have been made to use urethane in the construction of thin display panels, but no successes were reported by others before the filing of this disclosure. Urethane expands upon curing, and molds designed to make thin panels from urethane have proved to be unsatisfactory because the expansion of the foam simply destroys such molds. If the problem is solved by admitting very small quantities of urethane into the mold so that the subsequent expansion does not break the mold, the resulting panel has too many large voids therewithin for an acceptable product. The problem is so intractable that the conventional wisdom in the panel making and the urethane industries is that thin panels of the type having utility as display panels will never be made from urethane.
There is a need for a sturdy, light-in-weight display panel having a urethane foam core, but the prior art, when considered as a whole in accordance with the requirements of law, neither teaches nor suggests how the need could be fulfilled.
There is also a need for an improved way to hingedly interconnect the novel panels and display panels, in general.
The common hinge is well known, but it is unsatisfactory for use with display panels. It includes a central post having a round cross section and a pair of flat leaf members each of which has a plurality of cylindrical post-receiving members formed along a preselected edge thereof. The plural cylinders interleave with one another when the hinge is assembled and the post is slidably received within the bore collectively defined by said cylindrical members.
The common hinge is typically of metallic or plastic construction and as such is not flexible. Moreover, the common door hinge enables the hinged door to open in one direction only, i.e., the common hinge is not double acting. If the common hinge is employed to hingedly interconnect flat members such as display panels, the hinge will not only be visible and thus detract from the aesthetics of the display, but a pronounced seam between adjacent panels will also be visible.
There is a need, therefore, for a double acting hinge capable of interconnecting panels or other flat members in edge-to-edge relation to one another. The ideal hinge would also be hidden from view and would allow edge-connected panels to seamlessly abut one another, but the prior art, taken as a whole, neither teaches nor suggests how such a hinge could be provided.